This was discussed at the last O.D.O.T. Q&A meeting. I was a bit late and asked O.D.O.T. for the details in writing and a map. Here they are:

When the rehabilitation of the Abbey Avenue bridge is underway, one lane of the bridge will be closed and under construction. The remaining lane will be open for one-way traffic, westbound (or out of Tremont), with pedestrian traffic maintained on that same side.

The detour takes you north on W 20th Street and over the Lorain-Carnegie Bridge. Motorists may then enter I-90 westbound at E 9th Street and continue over the Innerbelt Bridge to enter Tremont at W 14th Street.

The one-way westbound condition provides a number of benefits:

• Construction materials and debris can be hauled away from the job site, without carrying it past most of the Tremont residential and business neighborhood.
• The detour route is on roadway already approved for use as a haul route, where the pavement is in good condition.
• The detour route is on roadway where there is adequate room for the extra traffic.
• The detour route avoids the three I-90 bridges in Tremont - Fairfield, Kenilworth and Starkweather. These bridges will all have active construction during the spring to fall 2012 construction season.
• The detour route avoids crossing an active railroad where motorists can be delayed by a train passing through, or a train moving through the switch to a destination.
• When we evaluated the eastbound one-way option, the potential detour would include narrow roads in terrible condition (Train), with an active train crossing, through the W 11th and W 14th residential and business neighborhoods, and would have to use a variety of crossings under I-90, through one of the three active construction sites for the three interstate overpass bridges (also under construction in 2012).